1. Field of the Invention
The present invention is directed generally to controlling the level of liquids particularly in fuel tanks and more specifically to a jet level sensor useful for detecting the liquid level in such fuel tanks.
2. Background of the Invention
It has long been desirable to control the level of liquid particularly in fuel tanks normally incorporated in aircraft. Such automatic level control systems normally will preclude overflow of the fuel tank with all of the attendant disadvantages thereof such as fire hazard, wasted fuel, bad odors and the like. Various types of systems have been developed to accomplish the desired level control such as traditional float operated mechanisms or jet level sensor systems or diaphragm operated valve systems. The present invention is directed specifically to jet level sensor systems and more particularly to the jet level sensor. Typical level control systems known to Applicant which employ jet level sensors are exemplified by U.S. Pat. Nos. 4,211,249; 3,269,404; 3,406,709; 4,312,373; 4,202,367; 4,161,188; 4,024,887; 3,817,246; 3,561,465; and 4,006,762. The present invention is an improvement over the system disclosed in U.S. Pat. No. 4,006,762 and the disclosure of U.S. Pat. No. 4,006,762 is incorporated herein by reference.
Jet level sensor control systems utilized in the prior art as exemplified by the above-identified patents have generally been satisfactory. However, some difficulties have been encountered whether the system uses single or dual jets for liquid sensing. Some of the difficulties encountered are (1) that the fuel in the tank will splash as the level thereof is increased and will sometimes interrupt the liquid jet in the jet level sensor thereby causing a condition of on-off, on-off indicators, sometimes referred to as "milking" until the fuel in the tank has reached the desired level, (2) that the recovery of the pressure present in the liquid jet is, in some instances, quite low resulting in unreliable operation of the sensing, and (3) that many of the prior art jet level sensors are rather complex and thus are expensive to manufacture and to maintain.